1. Field
Example embodiments relate to a composition containing thiazole rings, an organic semiconductor polymer containing the composition, an organic active layer containing the organic semiconductor polymer, an organic thin film transistor (OTFT) containing the organic active layer, an electronic device containing the OTFT, and a method of preparing the same. Other example embodiments relate to a composition containing thiazole rings of a structure, which contains hetero arylene or arylene showing p-type semiconductor property in addition to thiophene showing p-type semiconductor property and thiazole rings showing n-type semiconductor property at a polymer main chain, to thereby exhibit increased charge carrier mobility and decreased blocking leakage current when applied to an organic thin film transistor, an organic semiconductor polymer containing the composition, an organic active layer containing the organic semiconductor polymer, an OTFT containing the organic active layer, an electronic device containing the OTFT, and a method of preparing the same.
2. Description of the Related Art
An organic thin film transistor (OTFT) may include a substrate, a gate electrode, an insulating layer, a source-drain electrode and a channel layer, and may be a bottom contact (BC) type or a top contact (TC) type. The bottom contact (BC) type may form the channel layer on the source-drain electrode, and the top contact (TC) type may have a metal electrode formed through mask deposition on the channel layer.
The channel layer of the OTFT has been commonly made of an inorganic semiconductor material, e.g., silicone (Si). However, the use of such inorganic-based material may be economically unfavorable and may require a high temperature-high vacuum process. Thus, the inorganic-based material has been replaced by an organic-based material, in accordance with enlargement, cost-reduction and softening requirements of a display.
Research on an organic semiconductor material for a channel layer of an OTFT is in progress, and the property of a transistor using the same has been reported. Representative examples of the small molecular or oligomer organic semiconductor material, which has been studied, may include melocyanine, pthalocyanine, perylene, pentacene, C60 and/or thiophene oligomer, and the related art demonstrates an organic semiconductor material showing increased charge carrier mobility of about 3.2˜5.0 cm2/Vs or more by using pentacene crystals. Further, an increased charge carrier mobility of about 0.01˜0.1 cm2/Vs and current on/off ratio may be possible by using an oligothiophene derivative. However, the above-described techniques mainly form a thin film depending upon a vacuum process.
There have been numerous reports for an OTFT using a thiophene-based polymer as a polymer material. Such an OTFT does not show as improved properties as that using a relatively small molecular material, but has an advantage in that it is possible to process a relatively large area at reduced costs through a solution process, e.g., printing technique. A polymer OTFT device experimentally prepared by using F8T2 polythiophene material may exhibit about 0.01˜0.02 cm2/Vs of charge carrier mobility. As described above, although the organic semiconductor polymer material exhibits relatively lower properties of a TFT device, e.g., charge carrier mobility, than pentacene which is the relatively small molecular material, such material has advantages in that it does not require increased operation frequency and may be economically used in the fabrication of a TFT.
However, in order to commercialize an OTFT, important parameters, e.g., increased current on/off ratio and charge carrier mobility, must be satisfied. Leakage current under a blocking (off) condition should be reduced as much as possible.
The related art discloses that the combination of an n-type inorganic semiconductor material and a p-type organic semiconductor material as an active layer improves the parameters of an OTFT device. However, this process is still relatively difficult in mass-production because it is not different from the existing silicone-based TFT process requiring deposition. The related art also teaches an OTFT device having about 0.01˜0.04 cm2/Vs of charge carrier mobility which is prepared by using regioregular poly(3-hexylthiophene) (P3HT). However, because the representative regioregular poly(3-hexylthiophene) (P3HT) shows relatively increased charge carrier mobility of about 0.01 cm2/Vs, but its current on/off ratio is lower than 400 due to its increased blocking leakage current (about 10−9 A or more), its application to an electrical device may be limited.